1. Field of the Invention
The present invention relates to an ink jet recording head which has pressure producing chambers adapted to be pressurized by a pressure generator to jet ink droplets from nozzles.
2. Description of the Related Art
An ink jet recording head has a plate provided with a plurality of independent nozzles arranged in a row and a plurality of pressure producing chambers arranged in a row and connected to a common ink chamber. The inkjet recording head jets ink droplets from the nozzles by changing the volumes of the pressure producing chambers by piezoelectric vibrators or by vaporizing ink with heating devices.
The pressure producing chambers of the ink jet recording head must be arranged regularly at pitches corresponding to recording density. Therefore, the pressure producing chambers are formed by etching a plate or by an injection molding process using a polymeric material.
When it is desired to form the pressure chambers accurately in the plate by etching, an expensive silicon single crystal must unavoidably be used as the plate and the pressure producing chambers must be formed by anisotropic etching.
Although a plate of a polymeric material provided with pressure producing chamber can relatively easily be formed high accurately by an injection molding process, the plate is liable to be broken due to fatigue caused by repeated cyclic stress induced by piezoelectric vibrators or liable to be deteriorated by repeated heating by the heating devices.
The present invention has been made in view of the above-mentioned problems and it is therefore an object of the present invention to provide an ink jet recording head excellent in durability and capable of being manufactured at a low manufacturing cost.
According to a first aspect of the present invention, an ink jet recording head comprises an ink passage unit formed by superposing a nozzle plate, an ink passage plate and a cover plate, the nozzle plate being provided with a plurality of nozzles. The ink passage plate has a first surface and a second surface which are opposite to each other, and is provided with a plurality of pressure producing chambers connected to the nozzles respectively and with an ink reservoir communicating with the pressure producing chambers by means of a plurality of ink inlet ports. The cover plate is closely joined to the first surface of the ink passage plate. The ink jet recording head also comprises a pressure generator to apply pressure to an ink in the pressure producing chambers. The ink passage plate is made of a metal sheet having the first surface and the second surface, the ink reservoir is made by forming a through hole from the first surface to the second surface in the metal sheet, and the pressure producing chambers are made by forming a plurality of recesses in the first surface of the metal sheet by press working.
Preferably, the first surface of the metal sheet is subjected to a flattening process after the press working.
Preferably, a plurality of recesses forming the ink inlet ports and the recesses forming the pressure chambers are all formed simultaneously by the press working.
Preferably, the recesses forming the pressure producing chambers and the ink inlet ports are all formed in the first surface of the metal sheet.
Preferably, the recesses forming the ink inlet ports are shallower than the recesses forming the pressure producing chambers.
Preferably, the recesses forming the pressure producing chambers are formed in the first surface of the metal sheet, the recesses forming the ink inlet ports are formed in the second surface of the metal sheet, and the metal sheet is provided with connecting holes which enable the pressure producing chambers to communicate with the ink inlet ports respectively.
Preferably, both the first and the second surfaces of the metal sheet are subjected to a flattening process after the press working.
Preferably, a protuberance-forming recess is formed in the second surface of the metal sheet by the press working so that protruding portions are formed surrounding the recesses forming the pressure producing chambers when the recesses forming the pressure producing chambers are formed in the first surface of the metal sheet by the press working.
Preferably, a plurality of the protuberance-forming recesses formed in the second surface of the metal sheet are formed in a plurality of regions corresponding to a plurality of walls separating the adjacent pressure producing chambers respectively.
Preferably, a plurality of the protuberance-forming recesses formed in the second surface of the metal sheet are formed in a plurality of regions extending across the pressure producing chambers and a plurality of walls separating the adjacent pressure producing chambers respectively.
Preferably, the protuberance-forming recess formed in the second surface of the metal sheet is formed in a single region corresponding to all of the pressure producing chambers.
Preferably, the metal sheet is a sheet of pure nickel, a ternary alloy of zinc, aluminum and copper, or a superplastic alloy of lead, tin and bismuth or the like.
According to a second aspect of the present invention, an inkjet recording head comprises an ink passage unit formed by superposing a nozzle plate, an ink passage plate and a cover plate, the nozzle plate being provided with a plurality of nozzles. The ink passage plate has a first surface and a second surface which are opposite to each other and, is provided with a plurality of pressure producing chambers connected to the nozzles respectively and with an ink reservoir communicating with the pressure producing chambers by means of a plurality of ink inlet ports. The cover plate is closely joined to the first surface of the ink passage plate. The ink jet recording head also comprises a pressure generator to apply pressure to an ink in the pressure producing chambers. The pressure producing chambers are formed as a plurality of recesses formed in the first surface of the ink passage plate, the ink inlet ports are formed as a plurality of recesses formed in the second surface of the ink passage plate, and the ink passage plate is provided with a plurality of connecting holes which enable the pressure producing chambers to communicate with the ink inlet ports.
Preferably, the ink inlet ports and the pressure producing chambers are spaced apart in a direction along a thickness of the ink passage plate and partly overlap each other in a direction perpendicular to the direction along the thickness. The connecting holes are formed in portions of the ink passage plate where the ink inlet ports and the pressure producing chambers overlap each other.
According to a third aspect of the present invention, an ink jet recording head comprises an ink passage unit formed by superposing a nozzle plate, an ink passage plate and a cover plate, the nozzle plate being provided with a plurality of nozzles. The ink passage plate has a first surface and a second surface which are opposite to each other, and is provided with a plurality of pressure producing chambers connected to the nozzles respectively and with an ink reservoir communicating with the pressure producing chambers by means of a plurality of ink inlet ports. The cover plate is closely joined to the first surface of the ink passage plate. The ink jet recording head also comprises a pressure generator to apply pressure to an ink in the pressure producing chambers. The ink passage plate comprises a first sheet having the first surface and a second sheet having the second surface, the first sheet and the second sheet being superposed. The first sheet is provided with a plurality of through holes corresponding to the pressure producing chambers, a through hole corresponding to the reservoir, and a plurality of through holes forming the ink inlet ports. The ink inlet ports enable the through holes corresponding to the pressure producing chambers to communicate with the through hole corresponding to the reservoir. The second sheet is provided with a plurality of recesses forming the pressure producing chambers and a through hole forming the reservoir. The recesses forming the pressure producing chambers are connected to the through holes corresponding to the pressure producing chamber, and the through hole forming the reservoir is connected to the through hole corresponding to the reservoir.
Preferably, the second sheet is made of a metal sheet having a second surface and a third surface which are opposite to each other. The through hole forming the reservoir is formed from the second surface to the third surface in the metal sheet, and the recesses forming the pressure producing chambers are formed in the third surface of the metal sheet by a press working.
Preferably, the third surface of the metal sheet is subjected to a flattening process after the press working.
Preferably, a protuberance-forming recess is formed in the second surface of the metal sheet by the press working so that portions surrounding the recesses forming the pressure producing chambers are protruded when the recesses forming the pressure producing chambers are formed in the third surface of the metal sheet by the press working.
Preferably, a plurality of the protuberance-forming recesses formed in the second surface of the metal sheet are formed in a plurality of regions corresponding to a plurality of walls separating the adjacent pressure producing chambers respectively.
Preferably, a plurality of the protuberance-forming recesses formed in the second surface of the metal sheet are formed in a plurality of regions extending across the pressure producing chambers and a plurality of walls separating the adjacent pressure producing chambers respectively.
Preferably, the protuberance-forming recess formed in the second surface of the metal sheet is formed in a single region corresponding to all of the pressure producing chambers.
Preferably, the metal sheet is a sheet of pure nickel, a ternary alloy of zinc, aluminum and copper, or a superplastic alloy of lead, tin and bismuth or the like.
According to a fourth aspect of the present invention, an ink jet recording head comprises an ink passage unit formed by superposing a nozzle plate, an ink passage plate and a cover plate, the nozzle plate being provided with a plurality of nozzles. The ink passage plate has a first surface and a second surface which are opposite to each other, and is provided with a plurality of pressure producing chambers connected to the nozzles respectively and with an ink reservoir communicating with the pressure producing chambers by means of a plurality of ink inlet ports. The cover plate is closely joined to the first surface of the ink passage plate. The ink jet recording head also comprises a pressure generator to apply pressure to the ink in the pressure producing chambers. The ink passage plate is made of a metal sheet having a first surface and a second surface, the metal sheet comprising a through hole formed from the first surface to the second surface to form the reservoir. A plurality of recesses are formed in the first surface of the metal sheet to form the pressure producing chamber, and a recess is formed in the second surface.
Preferably, a plurality of the recesses formed in the second surface of the metal sheet are formed in a plurality of regions corresponding to a plurality of walls separating the adjacent pressure producing chambers respectively.
Preferably, a plurality of the recesses formed in the second surface of the metal sheet are formed in a plurality of regions extending across a plurality of walls separating the adjacent pressure producing chambers and the pressure producing chambers respectively.
Preferably, the recess formed in the second surface of the metal sheet is formed in a single region corresponding to all of the pressure producing chambers.
Preferably, the metal sheet is a sheet of pure nickel, a ternary alloy of zinc, aluminum and copper, or a superplastic alloy of lead, tin and bismuth or the like.
In the ink jet recording heads according to the first, second, third and fourth aspects of the present invention, it is preferable that the ink passage plate is provided with ink outlet holes in portions of bottom walls of the pressure producing chambers corresponding to the nozzles so as to connect the pressure producing chambers to the nozzles respectively.
In the ink jet recording heads according to the first, second, third and fourth aspects of the present invention, it is preferable that the cover plate is an elastic plate which is capable of being deformed at least in portions corresponding to the pressure producing chambers respectively. The pressure generator includes a plurality of piezoelectric vibrators which are capable of deforming the elastic plate.
According to the first aspect of the present invention, the ink passage plate is formed by forming a through hole for forming the reservoir and the recesses for forming the pressure producing chambers in the metal sheet by press working. Therefore, the pressure producing chambers of the ink passage plate, which significantly affect the ink jetting performance of the ink jet recording head, can accurately be formed in a desired size.
According to the second aspect of the present invention, the recesses forming the pressure producing chambers are formed in one of the surfaces of the ink passage plate and the recesses forming the ink inlet ports are formed in the other surface of the ink passage plate. Therefore, the recesses forming the pressure producing chambers and those forming the ink inlet ports can simultaneously be formed by press working using a pair of dies. Each of the pair of dies need not be provided with projections differing from each other in height and, consequently, accurate press working can be achieved.
According to the third aspect of the present invention, the first sheet provided with the through holes forming the ink inlet ports and the second sheet provided with recesses forming the pressure producing chambers are superposed to form the ink passage plate. Therefore, the ink inlet ports having a sectional shape of a desired shape can accurately be formed.